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It helps to know where the sunrise and sunset are going to occur, especially if you want to include a particular feature in your shot. This self-portrait was taken at sunrise in Capital Reef National Park. D1x, ISO 125, Nikkor 18-35mm.

Every serious outdoor photographer I know makes it a habit to head out armed with far more information about astronomical phenomenon than just sunrise and sunset times. Computers and the Internet have supplied a wealth of tools that you need to know about and start using. With them, you can find out the exact position (including altitude and azimuth) of the sun or moon at any time of the day, the phase of the moon, the location and totality of any eclipse, and much, much more.

Two types of tools are available for calculating useful data: computer programs and interactive Internet sites. Since the Internet sites are free and don't involve downloading or installing anything, let's look at them first. If all you want are some basic data points, here are two great starting places:

www.exptech.com/sunrise.htm
www.adventist.org/sun/

The Exptech calculator generates a very nice 10-day table, although it doesn't include azimuth or moon data. The Seventh Day Adventist site is useful for foreign locations--at least those where the church has a presence--as it sports a nicely handled "select a city" feature that fills in LongLat data for you.

If you need to calculate the sun's exact position at any given time--perhaps you're looking for when the sun might be perfectly located near a prominent local feature, like a mountain peak--try the NOAA solar position calculator. This tool, coupled with some map reading skills, can help you figure out exactly where the sun will be positioned in relationship to that geographic feature you're photographing.

But the most heavenly site for photographers (pardon the pun), is one sponsored by the US Navy. Here, you'll find virtually everything sun and moon related that you might ever want to know: sunrise, sunset, twilight, moonrise, moonset, transit times, moon phase, altitude and azimuth during a complete day cycle at intervals you select, equinox, solstice, perihelion, aphelion, Easter date, and a host of other wonderful calculators. Better still, you can obtain data for a single day, or for a month at a time. You may need to know the LongLat and Time Zone data for international locations and others that aren't near US cities, but the site has links to where you can find that information. Personally, I can't imagine any outdoor photographer venturing out on any serious shoot without first consulting the data on this site. More than once I've noticed something in the data that altered my shooting plans to incorporate the sun or moon.

Eclipses are also interesting celestial events, and many outdoor photographers like to plan them into their shoots, when possible. Did you know, for example, that there's a total solar eclipse that'll be perfect for incorporating Mt. Hood or perhaps Grand Teton National Park coming in August 2017? I didn't, at least until I discovered Fred Espenak's site. Fred works for the NASA Goddard Space Flight Center, and he keeps a page that predicts all solar eclipses out through 2030, including handy path maps and auxiliary data. Can't wait until 2017? Well, the site lists plenty of other eclipses you can chase, though you'll have to leave North America to get to most of them. (International Road Trip!)

On the software side, many Outdoor Photographer readers already know about Suntracker, the program that's used to generate the basic Almanac information in the back of each issue of the magazine. But the real joy for photographers is that very handy, portable versions of sun and moon info programs now exist. The two best I've found are these:

• For Palm Pilot Users: SOL! II is a $9.95 shareware program that has virtually all the information you'll ever need in the field. It also incorporates Location Manager, which allows you to download packages of LongLat data (or enter your own--why no one has put together a National Park set, I don't know; maybe I'll work on that in my spare time). One of the most interesting features of this program is the Find Time at Azimuth and Altitude feature, which can help you figure out when you need to be at a certain position to capture the sun at a designated spot in the sky.
  
• For Windows CE Users: Jonathan Sachs, the author of Lotus 1-2-3 and the excellent Picture Window image editing program, has written a utility called Ephemeris. This free program features some of the best laid out information I've seen on a handheld, and has arguably the easiest to use interface on any celestial calculation program. (To obtain it, go to www.dl-c.com and click on the downloads link, then click on the PC Freeware link).

Dozen's of other calculation programs exist for Windows and Macintosh users, but a few stand out:

• Moonrise is a $20 shareware product for Windows that provides all the most interesting moon and sun data, but can also print monthly tables including azimuth. Better still, when you register, you get a System Tray extension that graphically shows you the moon's phase and allows quick access to the program. Like Ephemeris, this program has a clean, easy to understand interface that doesn't get in your way, which is why I recommend it over other similar programs.
  
• A slightly nerdy, but free sunrise calculator is Sun Times. The graphical elements of this program can sometimes be useful in conjunction with topographical maps, as you calculate Dawn Lines and other interesting data in addition to the basic "sun's up," "sun's down" times.
  
• Mooncalc is a remarkable free DOS program that goes far beyond the usual rise/set, phase, and location data for sun and moon. It includes eclipse information, shows the position of the moon in relationship to a star chart (!), shows the orientation and position of moon craters for any observation site (!!), can correct for atmospheric refraction, and even can show you a map giving you the "earliest possible sighting."
  
• Macintosh users should take a look at the shareware product AllDay, now in version 5.1. This versatile calendar program can calculate virtually anything that revolves around dates, and provides sun and moon information for any location in the world.

Got a desire to "build your own?" Sky and Telescope magazine has published a wealth of program listings in BASIC over the years. The full set is available for download at http://www.skypub.com/resources/software/basic/basic.html/. One warning: these listings provide the basic calculations, but have virtually no user interface-you're on your own for making them pretty.

Don't forget that Casio Forester watch. It's hard to find at local stores (hint: try sporting goods stores catering to fishermen), but relatively easy to locate on the Web. I've since supplemented it with an expensive Suunto watch that provides altitude and a host of other data, but probably a better choice than loading up on watches is to get yourself a GPS device.

Virtually all of the Garmin and Magellan models now include basic sun and moon information, but they also provide accurate LongLat data to plug into your Palm Pilot or WindowsCE software, when needed. And since the government has recently turned off the random generator that kept personal GPS units from being perfectly accurate, you can now get excellent altitude measurements, as well (assuming you can see four or more satellites from your position).

Why do you want altitude information? Because in your location preparation you should be using a topographical map in conjunction with one of the aforementioned celestial calculators. For example, to figure out exactly where you need to be to get that perfect shot of the moon setting in the "crack" at the far western end of Yosemite valley, you need to be at a particular angle to the crack and a particular height to capture the moonset in the crack. Without the altitude information (and topo map), you'd only discover that shot by accident.

[Note: An article I wrote for Outdoor Photographer magazine deals with handling scene contrast at sunrise and sunset. The information you find here was condensed into a small sidebar due to lack of space. By all means, read that article, but don't forget that there is more detailed information about celestial calculations here.]

What's an Azimuth?
You probably already know the definitions for sunrise, sunset, moonrise, moonset, moon phase, and a number of other terms used by the tools described in the article in the left-hand column. But there's a few you may need some extra help understanding:

• Altitude: In the context of celestial calculations, the distance, expressed as an angle, at which a body appears above the horizon.
  
• Azimuth: The point at which a vertical line from a heavenly body intersects the horizon. Note that in astronomical measurements, the arc is measured from the South point, while in navigational measurements, it is from the North point. Make sure you know which one your tool is showing you.
  
• Dawn Line: A curved line applied to a map that shows the relative position of first light at any given time. Those clocks that show a world map of where the sun is currently up have moving dawn (and dusk) lines on them.
  
• Transit Time: The time at which a heavenly body crosses the meridian (mid-point in the sky) of a given location.
  
• Twilight: informally, the period of time when there is light in the sky before sunrise, or after sunset; officially, there is a standard by which twilight is calculated, so you'll often see Twilight Time calculated by programs. Generally it's hard to photograph at the beginning of twilight time in the morning--you usually need a bit more light to get exposures that won't involve reciprocity calculations on your part.